While the demands for greater engagement in science in general and regulatory science in particular have been steadily increasing, we still face limited understanding of the empirical resonance of these demands. Against this context, this paper presents findings from a recent study of a potential participatory opening of the German Federal Institute for Risk Assessment, a prominent regulatory scientific organization in the field of risk governance. Drawing upon quantitative surveys of the public and selected professional experts as well as in-depth (...) qualitative expert interviews, we identify a general support for greater engagement in science-based risk assessment. However, we also find significant contestation concerning its potential enactment and its normative and strategic merit. Underlying these contestations, we identify the persistence of a normal view of science and decisionist understanding of risk assessment, which create conflicting legitimacy demands for BfR and other regulatory scientific organizations. Together with concerns about imbalances in the power to participate, especially in highly specialized engagement processes, these pose significant challenges for the institutionalization of more participatory practices. (shrink)